Pacemaker Malfunction

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Pacemaker Malfunction
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ECG Signs of Pacemaker Malfunction

• Failure to output
• Failure to capture
• Undersensing
• Inappropriate pacemaker rate
• true malfunctions / pseudomalfunctions

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Failure to Output

• Causes
• Oversensing
• Battery depletion ( of time pacing is required,
  thresholds necessary, single- or dual-chamber
  pacing, rate-modulation and other features)
• Circuit failure (Lead fracture, disconnection of
  lead from the PM)
• Random component failure (rare)
• Pseudomalfunction
• Crosstalk (dual-chamber PM)
• when the monitor system does not display the
  pacemaker stimulus
• artifact when it is really present (frequently
  with bipolar pacing)

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Oversensing

• Unexpected sensing of an intracardiac or
  extracardiac signal.
• Intermittent or constant
• Electrical signals that may cause oversensing
  include myopotentials, T waves, and P
• waves.
• Oversensing of myopotentials in a single-chamber
  PM may result in pauses,
• whereas oversensing of myopotentials by the
  atrial-sensing circuit of a dual-
• chamber PM may result in rapid paced
  rhythms.
• Corrected by reprogramming the sensitivity or by
  reprogramming the refractory
• period of the channel on which oversensing is
  occurring
• Oversensing of extracardiac events occurs much
  less commonly with bipolar
• sensing.

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dual-chamber bipolar PM. Paced ventricular
activity is absent after the third paced atrial
beat because of oversensing
PM programmed to unipolar sensing. Sensing of
myopotentials led to symptomatic pauses.
Reprogramming the pacemaker to a bipolar sensing
prevented myopotential oversensing
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Cross talk

• Not a true malfunction
• In a dual-chamber PM, the PM stimulus in one
  chamber is sensed in
• the other chamber.
• For the PM-dependent patient, inhibition could
  result in ventricular asystole.
• Most PMs have two methods of protection
• Interposition of a short 'blanking period' of
  refractoriness in the ventricular channel
  simultaneous with the atrial output stimulus.
• Ventricular "safety pacing," whereby any event
  sensed on the ventricular sensing circuit within
  a defined early portion of the AV delay initiates
  the delivery of a ventricular pacing stimulus.

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DDD pacemaker. After the third atrial pacing
artifact, there is evidence of atrial
depolarization, but there is no ventricular
pacing output. Failure to deliver the ventricular
pacing artifact is due to crosstalk
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Failure to Capture

• Cause
• Dislodgment of the PM lead from the endocardial
  surface (usually in the first
• few weeks)
• Break in the insulation of the PM catheter allows
  some of the current from the
• electrode to escape into the surrounding
  tissues.
• Impending battery depletion
• If the pacing threshold required to depolarize
  the myocardium is greater than the programmed
  voltage amplitude and pulse duration (Poor lead
  position, exit block etc.)
• Marked metabolic abnormalities, such as
  hyperkalemia, and some cardioactive
• drugs, such as flecainide.
• Pseudomalfunction
• Inappropriately low voltage-amplitude and
  pulse-duration settings
• A PM artifact occurring within the myocardial
  refractory period

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DDDR pacemaker. All but one ventricular pacing
artifact fail to result in ventricular
depolarization, that is, failure to capture
Intermittent ventricular failure to capture in a
patient with a dual-chamber pacemaker
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Undersensing

• Intermittent or total
• Rarely an urgent problem
• Results in PM output that is undesirably
  competitive with the intrinsic rhythm.
• Can result in an unwanted rhythm (eg. atrial
  pacing that competes with NSR may
• result in AF).
• Competition in the ventricle is possible but is
  almost never a problem except when
• the fibrillation threshold has been altered by
  ischemia, electrolyte imbalance, or
• some other metabolic abnormality.
• Undersensing can frequently be corrected by
  reprogramming the sensitivity

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• Causes
• Lead dislodgment
• Poor lead position at the time of implantation
• Interruption in the insulation of the pacing
  catheter.
• Delivery of a low-amplitude P wave or QRS complex
  to a normally functioning
• pacing system. (eg. concomitant drug therapy,
  body position, MI, and
• cardiomyopathy)
• Pseudomalfunction
• Magnet application
• Environmental electrical noise
• When a P wave or QRS complex falls within the RP
  of PM
• Monitor artifact
• In dual-chamber PMs, apparent undersensing may
  occur during the initial portion of
• the AV interval (blanking period).
• During this interval, the ventricular channel of
  the pacemaker is refractory to avoid
• sensing of the atrial stimulus and
  depolarization. If an intrinsic ventricular event

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ventricular PM programmed to 50 bpm. The second
and third pacing artifacts occur inappropriately
close to the preceding QRS complex (that is, at
less than 1200 ms the programmed rate of the PM)
Functional undersensing. ventricular PM
programmed to 70 bpm. There is failure to capture
with the second and third pacing artifacts. The
third pacing stimulus occurs 850 ms after the
preceding intrinsic QRS (normal sensing). The
fourth pacing stimulus occurs 640 ms after the
preceding intrinsic QRS, indicating that the
preceding QRS complex was not sensed because it
occurred during the pacemaker's ventricular RP
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Inappropriate Pacing Rates

• Runaway pacemaker
• May be lethal for both PM-dependent and
  non-dependent patients.
• Pacing rates may be very rapid and cause
  hemodynamic instability and collapse.
• Result from battery failure, random component
  failure, or component failure
• induced by therapeutic radiation.
• Treatment is disabling the faulty pacemaker
  output
• Pseudomalfunction
• Sensing abnormalities
• Tracking of atrial fibrillatory or flutter waves
• PM re-entrant tachycardia (seen in dual-chamber
  PMs occurs when sensing of a
• retrograde atrial depolarization initiates
  ventricular pacing, which in turn leads
• to retrograde conduction and repetition of the
  cycle).
• Electromagnetic interference from the patient's
  environment may cause the
• generator to be reset to a rate different from
  that programmed.
• Many PMs operate at a slower rate when battery
  depletion is imminent.

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Pacemaker re-entrant tachycardia with a
dual-chamber PM. Atrial and ventricular pacing
stimuli precede the first three paced complexes
at a rate of 80 bpm. A PVC follows the third
paced ventricular complex and is conducted in a
retrograde to the atria. The atrial activation is
sensed by the PM and initiates ventricular
pacing. The pacing rate is limited to the
programmed upper rate limit of 110 bpm
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Environmental Causes of Pacemaker Malfunction

• Electrocautery
• Causes temporary sensing problems or
  reprogramming (rarely permanent alteration)
• Transthoracic Defibrillation
• Can cause reversion to back-up mode, transient
  increases in capture threshold
• and loss of capture as well as destruction of
  the PM generator and circuitry
• Damage is minimized by positioning paddles
  anteroposteriorly and as far from
• the pacemaker or lead as possible (ideally
  15cm).
• Extracorporeal Shock-Wave Lithotripsy
• Usually synchronized to the patient's ventricular
  depolarization or to the output
• stimulus of the PM.
• In dual-chamber PMs, synchronization of the
  lithotriptor with the atrial output
• can result in inhibition of ventricular output.
• In patients with an rate-adaptive PM, sensing of
  the shock waves can result in
• increased pacing rates and damage to the
  piezoelectric crystal.
• The following guidelines should be followed 1)
  Program the PM to the VVI or
• VOO mode 2) keep the focal point of the
  lithotriptor at least 6 inches away

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• Magnetic Resonance Imaging
• All pacemakers to revert to asynchronous mode
  because of reed-switch closure.
• Investigations have shown that MRI does not
  permanently damage the reed
• switch or other pulse generator components.
• The radiofrequency does not alter the acutely
  programmed variables, change the
• normal magnet rate, or induce pacing in most
  pacemakers tested.
• A study by Vahlhaus et al. of 32 patients with PM
  exposed to MRI at 0.5 Tesla.
• Lead impedance, sensing and stimulation
  thresholds did not change, battery
• current and impedance tended to increase, no
  change in programmed data or the
• ability to interrogate and program. No
  irreversible changes in PM systems
• 
  PACE 2001 24 489-95
• In general, MRI should be avoided in a patient
  with an implanted PM.
• MRI may be attempted in non-PM-dependent patients
  if the device can be
• programmed to an output at which there is
  failure to capture or OOO mode.
• Low magnetic field (0.5 Tesla) is preferable.
• The patient should be monitored by pulse
  oximetry, blood pressure and ECG

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• Transcutaneous Electrical Nerve Stimulation
• Appears to be safe in most patients with
  permanent PMs.
• It is not known how close to the PM the
  stimulator can be placed, and it is best
• to avoid applying the stimulator to a vector or
  path that would be parallel to the
• pacing lead.
• In patients with VD or DDD PMs, it may result in
  an increased ventricular rate.
• Therapeutic Radiation
• Failure of various battery components or
  accelerated battery depletion
• Changes in sensing capability, failure of
  telemetry function, runaway function
• and complete shut down may all occur
• No specific prediction relative to dose can be
  made.
• Particularly patients undergoing radiation for
  thoracic / chest wall malignancy.
• Precautions - Position the field of radiation at
  an angle oblique to the PM, total
• accumulated dosage limit of 2 rad, shielding of
  the PM with a 1cm margin may
• be required.
• If this is not possible, the PM should be
  explanted and moved to another site .

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• RFA
• PM should be checked before and after ablation.
• Rate response function should be turned off.
• RF applications should be as brief as possible
  and remote from the electrode tip.
• If the patient is not dependent, the pacemaker
  can be programmed to OOO or
• VVI at a lower rate than the intrinsic heart
  rate.
• If the patient is dependent, the PM should be
  programmed to VOO mode
• Uncommon sources of EMI
• dental instruments, including ultrasound scalers
  and cleaners, and electrosurgical instruments can
  cause transient inhibition of PM output
• Certain cardiac monitoring systems can cause
  inappropriate rate changes in
• patients with rate adaptive pacing systems that
  use a minute ventilation sensor.
• Antitheft devices may cause EMI with pacemakers.
• Acoustomagnetic systems may cause reversion to
  asynchronous pacing and
• rapid ventricular pacing.

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Nonmedical Equipment and Devices

• Cellular phones
• May interact with PM function by inhibiting the
  pacing output, asynchronous
• pacing and ventricular triggering.
• Hayes DL et al in a multicenter study studied 980
  patients.
• The incidence of all types of interference was
  20.
• Ventricular tracking of signals sensed on the
  atrial channel, noise reversion and
• inhibition of ventricular output were the most
  commonly observed.
• The incidence of overall clinical significant
  interference was 6.6 .
• Interference that was definitely clinically
  significant occurred in only 1.7 of
• tests and only when the phone was held over the
  pacemaker.
• Interference was more common in dual chamber
  systems (25.3 ) than in single
• chamber systems (6.8 ) and in digital
  telephones (24) compared to analog
• telephones (3 ).
• Patients who are PM dependent should use an
  analog type cellular phone
• system. Carrying the phone on the same side of
  the body as the implanted
• PM may cause interference. When using the phone,
  it should be held at
• least 15 cm away from the PM and on the opposite
  ear.
• N Eng J Med 1997 336 1473-9

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• Potentially significant restrictions exist for a
  small subset of patients
• who work in environments with equipment capable
  of causing
• significant electromagnetic interference eg.
  internal combustion
• engines, arc welding equipment, degaussing
  equipment and induction
• ovens.
• The use of bipolar leads can minimize or
  eliminate the problem.
• Microwaves should not cause any problem. Metal
  detectors could
• theoretically cause inhibition of a single beat,
  but significant clinical
• sequelae should not result.

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Triboelectric simulation

• Static electricity or triboelectric phenomena
  occur more commonly during
• very cold weather and very low relative
  humidity.
• Triboelectric signals are usually wider and more
  irregular than pacemaker
• stimuli
• Relatively prolonged overshoot is typical of
  electrostatic discharge

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• THANK YOU

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Pacemaker Syndrome

• First described in 1969 by Mitsui et al.
• Incidence ranges from 2 to 83.
• Defined as the symptoms associated with right
  ventricular pacing relieved with the
• return of A-V and V-V synchrony.
• The symptoms include DOE, PND, orthopnea,
  hypotension, pre-syncope, and
• syncope.
• Additional symptoms include easy fatigability,
  malaise, headache, and the sensation
• of fullness and pulsations in the head and neck
• Symptoms are most severe when intact V-A
  conduction is intact.
• Signs of congestive heart failure, cannon
  A-waves.